1. Field of the Invention
The present invention relates to a dispersant composition comprising at least one non-ionic surfactant and at least one polymer comprising at least one salt of a carboxylic acid group. The present invention further relates to a modified pigment composition and an aqueous coating composition comprising the dispersant compositions.
2. Description of the Related Art
Coating compositions are used for decorative, protective, and functional treatments of many kinds of surfaces. These surfaces include coils, metals, appliances, furniture, hardboard, lumber and plywood, marine, automobile, cans, and paperboard. Some coatings, such as those on undersea pipelines, are for protective purposes. Others, such as exterior automobile coatings, fulfill both decorative and protective functions. Still others provide friction control on boat decks or car seats. Some coatings control the fouling of ship bottoms, others protect food and beverages in cans. Silicon chips, printed circuit panels, coatings on wave-guide fibers for signal transmission, and magnetic coatings on videotapes and computer disks are among many so-called hi-tech applications for coatings.
Surface coating compositions are generally more or less viscous liquids with three base components: a film-forming substance or combination of substances called the resin or binder, a pigment or combination of pigments, and a volatile liquid. The combination of resin and volatile liquid is often referred to as the vehicle. Vehicles may be aqueous or non-aqueous and may be in a solution form or as a dispersion of fine binder particles in a non-solvent. The components and manufacturing of coating compositions such as aqueous coatings are further discussed in the Concise Encyclopedia of Polymers, Science and Engineering, pages. 160-171 (1990), which is incorporated herein by reference.
Pigments are finely divided, insoluble, solid particles dispersed in the coating vehicle and are distributed throughout the resin or binder in the final film. A wide variety of conventional black and colored pigments have been used in coating compositions. In addition, aqueous and non-aqueous inks and coating compositions comprising modified carbon products having attached organic groups are described in U.S. Pat. Nos. 5,672,198 and 5,713,988, both incorporated in their entireties herein by reference.
Surfactants may also be added to coating compositions to help improve performance. Typically, these surfactants are used in combination with the pigments of the coating compositions and, as such, are therefore referred to as dispersants. Several different classes or types of dispersants have been used in coating compositions. The choice of dispersant is dependent on a variety of factors, including the properties of the pigment, particle size, and the type of resin or binder. However, the dispersant can often have a negative impact on properties such as color development. Therefore, the amount of dispersant must be adjusted for the components used in order to obtain coating compositions with good overall properties.
Thus, while dispersants have been used in coating compositions, there remains a need for dispersant compositions which enable specific types of pigments to be dispersed in an aqueous vehicle while also resulting in good color performance.